1. Field of the Invention
This invention concerns the connection of multicore cables having a plurality of individual conductor screens to a connector body. The multicore cables to which the invention is applicable may have an individual electrically conductive screen for each conductor or individual electrically conductive screens may be provided for respective groups of conductors. The screened conductors or groups of conductors may be arranged within a collective screen.
2. Description of the Prior Art
Various proposals have been made for effecting connections between such a multicore cable and a connector body with provision for anchoring the conductor screens relatively to the connector body so as to miniraise mechanical loading of the cable conductors and, especially, to achieve electrical bonding of the individual screens to one another and to the connector body or a component associated therewith. In general these proposals involve the employment of a backshell having provision both for securing the cable in a manner to transmit mechanical loads and for obtaining electrical continuity between itself and the conductor screens of the cable.
One such proposal is represented by GB-A-2199198 that discloses a backshell having a cylindrical tubular body portion which in one embodiment includes an integral cylindrical end portion having a slot extending from one end and generally parallel to a longitudinal axis. The slot receives one end of an electrically conductive ribbon that is wound about the cable and in contact with the individual conductor screens. The end portion of the body is provided with an external coarse thread to receive an internally threaded termination nut which serves to trap a free end of the ribbon to provide good electrical continuity and axial restraint. The disclosed construction is complex and the requirement for the separate termination nut increases the weight.
In our co-pending application no. 9027024.0 (GB-A-2239358) we have disclosed backshell constructions that overcome certain problems of the prior art devices and that in preferred embodiments are simpler and lighter than the prior devices such as that exemplified by GB-A-2199198. The preferred backshell construction includes an electrically conductive tubular member having at least one aperture in the form of a hole having a continuous boundary. In use of this backshell construction, the individual conductor screens of the cable are exposed over a predetermined length of the latter and an electrically conductive ribbon is wound into contact with the corresponding portions of the length of each exposed conductor screen to provide a ribbon-wound portion of the length of the cable. The tubular member of the backshell is then positioned over the cable with the aperture in registration with the ribbon-wound portion of the cable length and the ribbon is passed through that aperture; the tubular member is then rotated relatively to the cable to wind the ribbon about the cable, whereafter the free end of the ribbon is wound about the exterior of the tubular member and secured in place as by a cable strap.
It is disclosed in our said application that when the tubular member of the backshell has apertures in the form of holes of appropriate dimensions, the wound ribbon tends to bulge into said holes to interfere with relative longitudinal motion between the cable and the tubular member. When the free end of the ribbon is wound about the tubular member and secured as with a cable strap, this portion of the ribbon bulges inwardly into the holes and engages the bulged portion of the ribbon within the tubular member to provide cable clamping and an efficient strain relief function.
We have now discovered that with a tubular member of appropriate configuration, winding of the ribbon about the cable until the wound ribbon tightly fills the space between the cable and the internal surface of the tubular member can in itself provide electrical continuity and sufficient anchorage for the cable to prevent its withdrawal from the tubular member, without the need for the free end of the ribbon to be wound about the exterior of the tubular member and to be secured thereto.